Attention is paid to a hologram which can record 2-dimensional data such as an image at a high density for high density information recording. The hologram has such a feature that a wave front of signal light which holds recording information is recorded onto a hologram recording medium by using an optical interference pattern with reference light as a diffraction grating. That is, an optical path of the reference light and that of the signal light are spatially separated and both of them are intersected in the hologram recording medium so as to be interfered, thereby recording the information.
By multiplex recording the optical interference patterns onto the hologram recording medium, a recording capacity can be remarkably increased. For example, in an angle multiplexing system, in the hologram recording medium upon recording, by changing an angle of the reference light to the signal light (also referred to an intersection angle) little by little and maintaining the angle for a predetermined time, the recording information which differs every angle can be multiplex recorded into the same area.
As shown in FIG. 1, in the case of executing the angle multiplex recording for recording a plurality of holograms to a same position on a hologram recording medium 2 while changing intersection angles Q1 to Qn of reference light RB1 to RBn for signal light SB1 to SBn which enter perpendicularly the hologram recording medium 2, an incident angle of the reference light is not continuously changed but it is necessary to repeat such an operation that the incident angle is fixed to a predetermined angle only for a time that is required for the recording at the intersection angle Q1, thereafter, is changed up to the intersection angle Q2 and fixed to a predetermined angle, subsequently, is moved up to the intersection angle Q3 and fixed to a predetermined angle, and holograms HG1 to HGn (diffraction gratings) are written.
For example, there is a method whereby by allowing a mirror for the reference light to execute the rotation and translation motion, the angle of the reference light which is irradiated to the hologram recording medium 2 is changed (refer to Patent Document 1).
There is also a method whereby by combining a galvano mirror and a telecentric optical system, the angle of the reference light is changed (refer to Patent Document 2).
When the angle multiplex recording of the holograms is executed, since an irradiation angle of the reference light is swung around a recording position of the hologram as a center, generally, in the hologram device of the angle multiplexing system, a light deflecting device constructed by what is called a 4f optical system and a galvano mirror GM is used as a mechanism for changing the angle of the reference light which is irradiated to the hologram recording medium. For example, as shown in FIG. 2, in the telecentric optical system in which a first lens L1 and a second lens L2 whose focal distances are equal (f1=f2) are arranged in a straight line on an optical axis, they are arranged so that a focal point at one end of the first lens L1 and that of the second lens L2 coincide, a rotary axis of the galvano mirror GM is arranged at the lens focal point (conjugate point) at one end, and the hologram recording medium 2 is arranged at the lens focal point (conjugate point) at the other end.    Patent Document 1: Japanese patent kokai No. 2004-69722    Patent Document 2: Japanese patent kokai No. 2005-310308